Module 3.pptx.............................

Amity School of Engineering & Technology B. Tech (CSE), Semester 6 Subject : Advanced Java Programming Course Code: IT404 Amity School of Engineering and Technology

2 What is Java Server Pages (JSP)? Java Server Pages (JSP) is a technology for developing web pages that support dynamic content. It helps to insert java code in HTML pages by making use of special JSP tags . Example <% …JSP Tag… %> JSP is a server-side program that is similar in design and functionality to java servlet . A JSP page consists of HTML tags and JSP tags . JSP pages are saved with .jsp extension 2

3 JSP vs Servlet 3

4 Comparing JSP with Servlet 4 JSP Servlet JSP is a webpage scripting language that generates dynamic content. Servlets are Java programs that are already compiled which also creates dynamic web content. A JSP technically gets converted to a servlet It embed the java code into HTML. E.g. <html> <% java code %> </html> A servlet is a java class. It put HTML into print statements. E.g. out.println (“<html code>”); JSPs are extension of servlets which minimizes the effort of developers to write User Interfaces using Java programming. A servlet is a server-side program and written purely in Java. JSP runs slower than servlet. As, it has the transition phase for converting from JSP to a Servlet. Once it is converted to a Servlet then it will start the compilation Servlets run faster than JSP In MVC architecture JSP acts as view . In MVC architecture Servlet acts as controller . We can build custom tags using JSP API We cannot build any custom tags in servlet.

5 Advantages of JSP over Servlets In a JSP page visual content and logic are separated, which is not possible in a servlet. i.e. JSP separates business logic from the presentation logic . Servlets use println statements for printing an HTML document which is usually very difficult to use. JSP has no such tedious task to maintain. 5

6 question 6 1. List advantages of JSP over Servlet.[3] Win’17 Win’18

7 Life Cycle of JSP 7

8 Life Cycle of JSP A JSP life cycle can be defined as the entire process from its creation till the destruction. It is similar to a servlet life cycle with an additional step which is required to compile a JSP into servlet . A JSP page is converted into Servlet in order to service requests. The translation of a JSP page to a Servlet is called Lifecycle of JSP . 8

9 Life Cycle of JSP 9 jspInit() _jspService() jspDestroy() Request Response Called only once Called only once Handles multiple request/response

10 Life Cycle of JSP JSP Lifecycle steps Translation of JSP to Servlet code. Compilation of Servlet to bytecode. Loading Servlet class. Creating servlet instance. Initialization by calling jspInit() method Request Processing by calling _jspService() method Destroying by calling jspDestroy() method 10

11 JSP Processing Life Cycle 11 hello.jsp hello_jsp.java Web Server Web Container hello_jsp.class Loading Servlet Class jspInit() _jspService() jspDestroy() Step:1 Translation from .jsp to servlet(.java) Step:2 Compilation of Servlet to bytecode Step:3 Step:4 Step:5 Step:6 Creating Servlet Instance Step:7

12 Life Cycle of JSP Web Container translates JSP code into a servlet source(.java) file. Then compiles that (.java) into a java servlet class ( bytecode ) . In the third step, the servlet class bytecode is loaded using classloader in web container. The Container then creates an instance of that servlet class. The initialized servlet can now service request. For each request the Web Container call the _jspService() method. When the Container removes the servlet instance from service, it calls the jspDestroy() method to perform any required clean up. 12

13 JSP Processing The following steps explain how the web server creates the web page using JSP: Web browser sends an HTTP request to the web server requesting JSP page. E.g. http://localhost:8080/1.jsp Web server recognizes that the HTTP request by web browser is for JSP page by checking the extension of the file (i.e .jsp) Web server forwards HTTP Request to JSP engine. The JSP engine loads the JSP page from disk and converts it into a servlet content. The JSP engine compiles the servlet into an executable class and forwards the original request to a servlet engine. 13

14 JSP Processing Servlet engine loads and executes the Servlet class. Servlet produces an output in HTML format. Output produced by servlet engine is then passes to the web server inside an HTTP response. Web server sends the HTTP response to Web browser in the form of static HTML content. Web browser loads the static page into the browser and thus user can view the dynamically generated page. 14 “Except the translation phase, a JSP page is handled exactly like a Servlet”

15 JSP Processing Translation Time Time taken to generate Java Servlet (.java) from .jsp file is termed as Translation Time . Request Time Time taken to invoke a Servlet to handle an HTTP request is termed as Request Time . 15

16 JSP Elements 16

17 JSP Elements 17 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

18 JSP Elements 18 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

19 JSP Scripting Elements 19

20 JSP Scripting Elements The scripting elements provides the ability to insert java code inside the jsp . There are three types of traditional scripting elements: scriptlet tag expression tag declaration tag 20 JSP Scripting Elements Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting

21 JSP Elements 21 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

22 scriptlet A scriptlet tag is used to execute java source code in JSP . A scriptlet can contain Any number of JAVA language statements Variable Method declarations Expressions that are valid in the page scripting language Syntax <% // java source code %> Example <% out.print("welcome to jsp"); %> <% int a=10; %> 22

23 scriptlet Everything written inside the scriptlet tag is compiled as java code. JSP code is translated to Servlet code, in which _jspService() method is executed which has HttpServletRequest and HttpServletResponse as argument. JSP page can have any number of scriptlets , and each scriptlets are appended in _jspService (). 23

24 First jsp program: First.jsp using scriptlet <html> <body> <%out.println( "Hello World! My First JSP Page" );%> </body> </html> 24

25 JSP Elements 25 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

26 expression The code placed within JSP expression tag is written to the output stream of the response . So you need not write out.print() to write data. It is mainly used to print the values of variable or method. Syntax <%=statement %> Example <%= (2*5) %> “ Do not end the statement with semicolon in case of expression tag. “ 26 turns out as out.print((2*5));

27 JSP Elements 27 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

28 declaration The JSP declaration tag is used to declare variables and methods The declaration of jsp declaration tag is placed outside the _jspService() method. Syntax <%! variable or method declaration %> Example <%! int a = 10; %> <%! int a , b , c ; %> <%! Circle a = new Circle(2.0); %> 28

29 JSP Elements 29 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

30 comments The comments can be used for documentation. This JSP comment tag tells the JSP container to ignore the comment part from compilation. Syntax <%-- comments --%> 30 JSP comment <%-- jsp comment --%> Java comment /* java comment */ or // for single line Html comment

31 Scripting Elements: Example <html> <body> <%-- comment:JSP Scipting elements --%> <%! int i =0; %> <% i ++; %> Welcome to world of JSP! <%= "This page has been accessed " + i + " times" %> </body> </html> 31 declaration scriptlet expression

32 JSP Elements 32 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

33 JSP Directives JSP directives provide directions and instructions to the container, telling it how to translate a JSP page into the corresponding servlet . A JSP directive affects the overall structure of the servlet class. JSP engine handles directives at Translation time . There are two types of directives: page directive include directive Syntax <%@ directive attribute="value" %> 33

34 JSP Elements 34 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

35 JSP Directives page directive 35

36 page directive The page directive defines attributes that apply to an entire JSP page. You may code page directives anywhere in your JSP page. By convention , page directives are coded at the top of the JSP page. Syntax <%@page attribute="value" %> Example <%@page import= "java.util.Date,java.util.List,java.io.*" %> <%@page contentType= "text/html; charset=US-ASCII" %> 36

37 page directive Attributes of JSP page directive import contentType extends info 37 Used to import class, interface or all the members of a package <%@ page import =" java.util.Date " %> Today is: <%= new Date() %> The contentType attribute defines the MIME type of the HTTP response. The default value is "text/ html;charset =ISO-8859-1". <%@ page contentType =application/ msword %> The extends attribute defines the parent class that will be inherited by the generated servlet <%@ page extends =" javax.servlet.HttpServlet " %> This attribute simply sets the information of the JSP page which is retrieved later by using getServletInfo () . <%@ page info =“Authored by : AuthorName " %>

38 page directive buffer language isELIgnored autoFlush 38 The buffer attribute sets the buffer size in kb to handle output generated by the JSP page. The default size of the buffer is 8Kb. <%@ page buffer ="16kb" %> <%@ page buffer ="none" %> The language attribute specifies the scripting language used in the JSP page. The default value is "java". <%@ page language ="java" %> We can ignore the Expression Language (EL) in jsp by the isELIgnored attribute. By default its value is false i.e. EL is enabled by default. <%@ page isELIgnored ="true" %> //Now EL will be ignored The autoFlush attribute specifies whether buffered output should be flushed automatically when the buffer is filled.Bydefault it is true. <%@ page autoFlush ="true" %>

39 page directive isThreadSafe session pageEncoding errorPage isErrorPage 39 This option marks a page as being thread-safe. By default, all JSPs are considered thread-safe(true). If you set the isThreadSafe = false, the JSP engine makes sure that only one thread at a time is executing your JSP. <%@ page isThreadSafe ="false" %> The session attribute indicates whether or not the JSP page uses HTTP sessions. <%@ page session ="true" %> //Bydefault it is true We can set response encoding type with this page directive attribute, its default value is “ISO-8859-1”. <%@ page pageEncoding ="US-ASCII" %> It is used to define the error page, if exception occurs in the current page, it will be redirected to the error page. <%@ page errorPage ="myerrorpage.jsp" %> The isErrorPage attribute is used to declare that the current page is the error page. <%@ page isErrorPage ="true" %>

40 JSP Elements 40 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

41 JSP Directives include directive 41

42 include directive JSP include directive is used to include the contents of another file to the current JSP page during translation time. The included file can be HTML, JSP, text files etc. Advantage of Include directive Code Reusability Syntax <%@ include attribute= "value" %> Example <%@ include file= "1.jsp" %> 42

43 JSP Implicit Object 43

44 Jsp Implicit Objects There are 9 jsp implicit objects . These objects are created by the web container that are available to all the jsp pages. 44 Implicit Object Type out JspWriter exception Throwable request HttpServletRequest response HttpServletResponse config ServletConfig session HttpSession pageContext PageContext page Object application ServletContext

45 Jsp Implicit Objects: out 45 For writing any data to the buffer, JSP provides an implicit object named out . It is an object of JspWriter. PrintWriter out= response.getWriter(); response.setContentType ( “text/html” ); out.print( “DIET” ); <html> <body> <% out.print ( “DIET” ); %> </body> </html> Servlet Code JSP Code

46 Jsp Implicit Objects: request Instance of javax.servlet.http.HttpServletRequest object associated with the request. Each time a client requests a page the JSP engine creates a new object to represent that request. The request object provides methods to get HTTP header information including from data, cookies, HTTP methods etc. 46

47 Jsp Implicit Objects: request Resquest.html <form action= " welcome.jsp " > Login: <input type= "text" name= "login" > <input type= "submit" value= "next" > </form> Welcome.jsp hello, <% out.println ( request.getParameter ( "login" )); %> 47

48 Jsp Implicit Objects: response The response object is an instance of a javax.servlet.http.HttpServletResponse object. Through this object the JSP programmer can add new cookies or date stamps, HTTP status codes, redirect response to another resource, send error etc. 48

49 Jsp Implicit Objects: response Response.html <form action= "welcome.jsp" > <input type= "text" name= "login" > <input type= "submit" value= "next" > </form> Welcome.jsp <% response.sendRedirect( "www.darshan.ac.in" ); %> 49

50 Jsp Implicit Objects: config config is an implicit object of type javax.servlet.ServletConfig. This object can be used to get initialization parameter for a particular JSP page. Config.html <form action= "MyConfig" > Login: <input type= "text" name= "login" > <input type= "submit" value= "sign_in" > </form> 50

51 Jsp Implicit Objects: config web.xml <servlet> <servlet-name> MyConfig </servlet-name> <jsp-file> /MyConfig.jsp </jsp-file> <init-param> <param-name> College </param-name> <param-value> DIET </param-value> </init-param> </servlet> <servlet-mapping> <servlet-name> MyConfig </servlet-name> <url-pattern> /MyConfig </url-pattern> </servlet-mapping> 51

52 Jsp Implicit Objects: config MyConfig.jsp <% out.print( "Welcome " +request.getParameter( "login" )); String c_name=config.getInitParameter( "College" ); out.print( "<p>College name is=" +c_name+ "</p>" ); %> 52

53 Jsp Implicit Objects: session In JSP, session is an implicit object of type javax.servlet.http.HttpSession . The Java developer can use this object to set, get or remove attribute or to get session information. MySession.html <form action= "MySession1.jsp" > <input type= "text" name= "uname" > <input type= "submit" value= "go" ><br/> </form> 53

54 Jsp Implicit Objects: session MySession1.jsp <html> <body> <% String name=request.getParameter("uname"); out.print("Welcome "+name); session.setAttribute("user",name); %> <a href= "MySession2.jsp" > next page </a> </body> </html> 54

55 Jsp Implicit Objects: session MySession2.jsp <html> <body> <% String name= (String)session.getAttribute("user"); out.print("Hello "+name); %> </body> </html> 55

56 Jsp Implicit Objects: pageContext Instance of javax.servlet.jsp.PageContext The pageContext object can be used to set , get or remove attribute. The PageContext class defines several fields, including PAGE_SCOPE, REQUEST_SCOPE, SESSION_SCOPE , and APPLICATION_SCOP E, which identify the four scopes. 56

57 Jsp Implicit Objects: pageContext Context1.jsp <% pageContext.setAttribute ( "user" , "name" ,PageContext. APPLICATION_SCOPE ); %> <a href= "Context2.jsp" > next page </a> Context2.jsp <% String name= (String)pageContext.getAttribute ( "user" ,PageContext. APPLICATION_SCOPE ); out.print( "Hello " +name); %> 57

58 Jsp Implicit Objects: page This object is an actual reference to the instance of the page. It is an instance of java.lang.Object Direct synonym for the this object. Example: returns the name of generated servlet file <%= page.getClass().getName() %> 58

59 Jsp Implicit Objects: application Instance of javax.servlet.ServletContext The instance of ServletContext is created only once by the web container when application or project is deployed on the server. This object can be used to get initialization parameter from configuration file (web.xml). This initialization parameter can be used by all jsp pages. <% //refers to context parameter of web.xml String driver=application.getInitParameter( "name" ); out.print( "name is=" +driver); %> 59

60 Jsp Implicit Objects: exception exception is an implicit object of type java.lang.Throwable class. This object can be used to print the exception. But it can only be used in error pages. <%@ page isErrorPage = "true" %> <html> <body> Sorry following exception occured: <%=exception %> </body> </html> 60

61 JSP Elements 61 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

62 Actions JSP actions use constructs in XML syntax to control the behavior of the servlet engine. We can dynamically insert a file, reuse JavaBeans components, forward the user to another page, or generate HTML for the Java plugin. Syntax <jsp:action_name attribute= "value" /> 62

63 JSP Elements 63 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

64 <jsp:param> This action is useful for passing the parameters to other JSP action tags such as JSP include & JSP forward tag. This way new JSP pages can have access to those parameters using request object itself. Syntax < jsp:param name = "name" value= "value" /> Example < jsp:param name = "date" value= "12-02-2018" /> < jsp:param name = "time" value= "10:15AM" /> < jsp:param name = "data" value= "ABC" /> 64

65 JSP Elements 65 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

66 <jsp:include> The jsp:include action tag is used to include the content of another resource it may be jsp, html or servlet. The jsp:include tag can be used to include static as well as dynamic pages 66 Attribute Description page The relative URL of the page to be included. flush The boolean attribute determines whether the included resource has its buffer flushed before it is included. By default value is false .

67 <jsp:include> Syntax <jsp:include page= "relative URL" flush= "true" /> Example <jsp:include page= "Action1.jsp" flush= "true" > <jsp:param name= "roll_no1" value= "401" /> </jsp:include> 67

68 JSP Elements 68 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

69 <jsp:forward> forwards the request and response to another resource. Syntax <jsp:forward page= "Relative URL" /> Example <jsp:forward page = "Action2.jsp" > <jsp:param name = "roll_no" value = "301" /> </jsp:forward> 69

70 JSP Elements 70 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

71 <jsp:plugin> This tag is used when there is a need of a plugin to run a Bean class or an Applet. The <jsp:plugin> action tag is used to embed applet in the jsp file. The <jsp:plugin> action tag downloads plugin at client side to execute an applet or bean. Syntax <jsp:plugin type= "applet|bean" code= "nameOfClassFile" codebase= "URL" /> 71

72 <jsp:plugin> MyApplet.java import java.applet .*; import java.awt .*; public class MyApplet extends Applet { public void paint(Graphics g) { g.drawString ( "Welcome in Java Applet." ,40,20); }} MyPlugin.jsp <html> <body> < jsp:plugin type= "applet" code= " MyApplet.class " codebase= "/ JSPClass / MyApplet " /> </body></html> 72

73 JSP Elements 73 JSP Element JSP Directives JSP Scripting Elements Actions page include Traditional Modern scriptlet expression declaration comments (html, jsp,java) EL Scripting <jsp:param> <jsp:include> <jsp:forward> <jsp:plugin>

74 EL Scripting Expression Language(EL) Scripting. It is the newly added feature in JSP technology version 2.0. The purpose of EL is to produce script less JSP pages. Syntax ${expr} Example 74 ${a=10} 10 ${10+20} 30 ${20*2} 40 ${10==20} false ${'a'<'b'} true EL output

75 EL Implicit Object 75 pageScope It is used to access the value of any variable which is set in the Page scope requestScope It is used to access the value of any variable which is set in the Request scope. sessionScope It is used to access the value of any variable which is set in the Session scope applicationScope It is used to access the value of any variable which is set in the Application scope pageContext It represents the PageContext object.

76 EL Implicit Object 76 param Map a request parameter name to a single value header Map containing header names and single string values. paramValues Map a request parameter name to corresponding array of string values. headerValues Map containing header names to corresponding array of string values. cookie Map containing cookie names and single string values.

77 EL Implicit Object An expression can be mixed with static text/values and can also be combined with other expressions Example ${param.name} ${sessionScope.user} 77 Impicit object Parameter Name Impicit object Parameter Name

78 EL Implicit Object: Example <form action= "EL1.jsp" > Enter Name :<input type= "text" name= "name" > <input type= "submit" value= "go" > </form> 78 1. Welcome, ${ param.name } EL.jsp EL1.jsp

79 EL Implicit Object: Example <form action= "EL2.jsp" > <% Cookie ck= new Cookie( "c1" , "abc" ); response.addCookie(ck); session.setAttribute( "sid" , "054" ); //for session %> Enter Name: <input type= "text" name= "name" > Enter Address: <input type= "text" name= "address" > <input type= "submit" value= "submit" > </form> 79

80 EL Implicit Object: Example <p> Name is : ${param.name} </p> <p> Address is : ${param.address} </p> <p> Cookie Name : ${cookie.c1.name} </p> <p> Cookie value : ${cookie.c1.value} </p> <p> Session id : ${sessionScope.sid} </p> 80 EL.jsp EL2.jsp

81 JSP EL Operator JSP EL Arithmetic Operators Arithmetic operators are provided for simple calculations in EL expressions. They are +, -, *, / or div, % or mod. JSP EL Logical Operators They are && (and), || (or) and ! (not). JSP EL Relational Operators They are == (eq), != (ne), < (lt), > (gt), <= (le) and >= (ge). 81

82 JSP EL Important Points EL expressions are always within curly braces prefixed with $ sign, for example ${expr} We can disable EL expression in JSP by setting JSP page directive isELIgnored attribute value to TRUE. <%@ page isELIgnored="true" %> JSP EL can be used to get attributes, header, cookies, init params etc, but we can’t set the values. JSP EL implicit objects are different from JSP implicit objects except pageContext JSP EL is NULL friendly, if given attribute is not found or expression returns null, it doesn’t throw any exception. 82

83 JSP with JDBC <% @page import="java.sql.*" %> <% Class.forName( "com.mysql.jdbc.Driver" ); Connection con=DriverManager.getConnection( "jdbc:mysql://localhost:3306/GTU" , "root" , "root" ); Statement stmt=con.createStatement(); ResultSet rs=stmt.executeQuery( "select * from diet" ); while (rs.next()) { out.println( "<p>" +rs.getString(1)); out.println(rs.getString(2)); out.println(rs.getString(3)+ "</p>" ); } con.close(); %> 83

84 JSP Session and Cookies Handling 84

85 JSP Cookie Handling Cookies are text files stored on the client computer and they are kept for various information tracking purpose. JSP transparently supports HTTP cookies using underlying servlet technology. 85

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